$.fn.extend({
    lazyload(){
       $(window).scroll(function(){
        let h1=window.innerHeight||document.documentElement.clientHeight
        let h2=document.body.scrollTop||document.documentElement.scrollTop
        let height=h1+h2
        $(this).Each((index,item)=>{
            let h=item.offsetTop
            if(h<=height){
                let data=$('item-img')
             $(item).attr("src","data")
            }
        }) 
    })
    }
})